What function does fascia serve in roofing structures?

Fascia plays a crucial role in roofing structures by serving as a protective and aesthetic covering for the ends of rafters or the sub-fascia. Positioned along the edge of the roof, fascia boards not only contribute to the overall appearance of the building but also help to safeguard the roof's underlying components from weather damage and pests. By capping off the rafters, they provide a certain level of defense against moisture infiltration, which can lead to rot and structural inefficiency. This protective function is essential for maintaining the longevity and integrity of the roofing system.

In comparison, the other options do not accurately reflect the primary function of fascia. Insulation is the job of materials specifically designed for thermal resistance, while fascia enhances the roof's visual appeal rather than being solely decorative. While fascia can contribute to the overall stability of the roof's edge, it does not serve as the main structural support; that role is typically fulfilled by other components like rafters and trusses. Thus, option C correctly identifies the primary function of fascia in roofing structures.